a(n) = 6*a(n-2) + a(n-4), where a(0) = 5, a(1) = 8, a(2) = 30, a(3) = 49.

Terms

a(0) =5a(1) =8a(2) =30a(3) =49a(4) =185a(5) =302a(6) =1140a(7) =1861a(8) =7025a(9) =11468a(10) =43290a(11) =70669a(12) =266765a(13) =435482a(14) =1643880a(15) =2683561a(16) =10130045a(17) =16536848a(18) =62424150a(19) =101904649a(20) =384674945a(21) =627964742a(22) =2370473820a(23) =3869693101a(24) =14607517865a(25) =23846123348a(26) =90015581010a(27) =146946433189a(28) =554701003925